Present methods to gather in-situ meteorological data include launching conventional balloon-borne rawinsondes, launching dropsondes from specially-equipped aircraft, using a calibrated pacer air vehicle, or flying specific flight patterns. The major drawbacks affecting these approaches can include spatial inaccuracy (in the case of balloon-borne or falling sensors), asset availability (in the case of dedicated measurement aircraft), and simple inefficiency. An in-situ radiosonde system capable of deployment from nearly any military aircraft would solve the problems of spatial inaccuracy, asset availability and simple inefficiency by allowing for the spatially and temporally precise deployment of sensors in the test airspace without placing any undue burden on other range assets or requiring additional flight time from the test aircraft.
One solution involves a system that is compatible with a countermeasures dispensing system and flare magazine that employ components common with current decoys and that follow the same trajectory upon deployment. These systems would be capable of operation as either a dropsonde or upsonde (rawinsonde), enabling measurements above or below the launch aircraft flight path; measure meteorological variables including pressure, temperature, relative humidity, and winds (the latter via GPS); and return data via one or more data link paths to either aircraft- or ground-based receivers.
The system would thus include an easily-deployed sonde which can either fall below (dropsonde) or rise above (upsonde) the flight path of the deploying aircraft, such as an F-16. Aircraft-based deployment ensures timely and spatially precise deployment of sensors. Furthermore, by using common countermeasures systems as the deployment mechanism, readily available chase aircraft can be used to gather the meteorological data immediately before a test.
Several challenges are faced in the deployment of sondes from countermeasure dispensing systems. The first challenge is that countermeasure systems are small due to the limited space on military aircraft. Another challenge in the development of a upsonde system is the necessity of being able to rapidly fill a balloon, such as a weather balloon, with hydrogen gas (H2) so that the upsonde can begin rising immediately after being deployed from the aircraft.
Hydrogen gas (H2) is the gas of choice for filling sondes. There are many ways to form hydrogen gas, and the selection of the gas generation method can depend on the specific application for which the gas is being generated. While few applications have a need to generate the gas quickly and from a housing as small as the countermeasures system, there is still another application with strict constraints, namely man-portable applications. There are many remote areas in the world where it is impractical or impossible to transport hydrogen or helium cylinders, or set up hydrogen generators. Furthermore, in some cases, a single person may be charged with launching meteorological balloons from areas reached only on foot or by parachuting into a location. In such a situation, the most compact and light-weight hydrogen generator possible is required.
Several hydrogen-generating technologies have been considered for the rapid generation of hydrogen gas, particularly for use in meteorological balloons.
The electrolysis of water can generate hydrogen to fill balloons. Key disadvantages of this approach include the need for external electrical power, pure water, size and weight of the equipment, and the relatively slow rate of the electrolytic reaction. A remote electrolysis system would require batteries and water to generate hydrogen gas to fill a balloon.
Methanol can be catalytically reformed, usually in the presence of water, to produce a mixture of hydrogen and either carbon monoxide or carbon dioxide. The resulting gas can be used as-is or the hydrogen can be separated to fill a meteorological balloon. Disadvantages ofthis approach include the size and weight of the equipment, and the need for precise thermal control of the catalytic reactor. The catalytic reaction occurs at about 230 degrees Celsius, which is a reasonable temperature to achieve. However, several problems present themselves with regard to a miniaturized approach, including maintaining the catalyst conditioning in storage (such as, kept under a hydrogen atmosphere), having a large enough reactor bed to achieve sufficiently fast hydrogen generation, driving a methanol/water solution through the reactor bed, and preheating the methanol/water solution to a vapor at 230 degrees Celsius.
Ammonia can be catalytically decomposed to yield hydrogen and nitrogen; this approach has been used for generating hydrogen at remote sites because it is easier to ship ammonia than hydrogen. Key disadvantages ofthis approach include size and weight of the equipment, as well as the comparatively demanding need to store ammonia in liquid forms in cases where volume is at a premium. Furthermore, catalytic decomposition of ammonia to nitrogen and hydrogen was examined, but either requires high temperatures (approximately 350 degrees Celsius) or relies on novel, still-experimental catalysts active at lower temperatures.
What is needed is a method and system that can generate hydrogen gas very quickly and fit in a very small volume. While methods to simply generate hydrogen gas are many, none of the systems can generate hydrogen gas rapidly from a lightweight, small volume system.